Intro to Hyd Symbols (1)

8/18/2019 Intro to Hyd Symbols (1)

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Graham Spencer Festo Didactic 02.02.2010 1

Basic Principles of

Hydraulics

Symbols

Page 19

مهندسي ر نش هيدروليك سهند شرك

هيدروليك

سيستمه ي

س خت

و

طر حي

تبريز – ير ن

:09144142432تلفن همر ه

فكس

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2/51


Symbols

Fixed Displacement One direction of flow. Constant delivery for

constant speed

Variable Displacement One direction of flow. Variable delivery for

constant speed

Directional of flow reversible. Variable

delivery for constant speed.

Pumps

Pressure compensated variable pump

One direction of flow, adjustable spring and

pump case drain.

Method of adjustment is shown on the arrow

Hydraulic Energy Source

(simplified representation)Page 21


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Symbols

Motors

Fixed Displacement

Variable Displacement

One direction of rotation.

Constant shaft speed for

constant flow rate

Either direction of rotation, depending ondirection of flow. Constant shaft speed for

constant flow rate.

Either direction of rotation.

Speed variable for constantflow.

Electric Motor

Engine

M

M

Drive units

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Symbols

Semi rotary

actuator Limited rotary movement eg

1800

x y

Equipment to

transform a

pressure x in to

a pressure y

Single acting

Continuous

Pressure Intensifiers

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Actuators

Symbols

Single Acting Returned by external force

Spring return

Vent

Telescopic Cylinder

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Actuators

Symbols

Double acting Double ended piston rod

Cushioned Variable cushioning at both ends.

Double acting Forward and return stroke under power

Single piston rod.

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DirectionalControl Valves

Symbols

Porting

(2 position)

Two Way2/2 way valve

Normally closed

Three

Way

3/2 way valve

Normally closed

Four Way4/2 way valve

Changeover

A

P

A

P T

A B

P T

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Valve Description

Number of Ports 3

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Number of

Control positions

Number of Ports 3

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Valve Description


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(Number of Boxes)

2Number of Controlpositions

Number of Ports 3

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Valve Description


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Method of

Operation

Push

Button

(Number of Boxes)


Number of Ports 3

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Valve Description


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Method ofReturn Spring

Method of

Operation

Push

Button

(Number of Boxes)


Number of Ports 3

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Valve Description


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Method ofReturn Spring

Method of

Operation

Push

Button

(Number of Boxes)


Number of Ports 3

Normally closedor Normally open

Flow path

blocked when

valve is at rest

Flow path

open when

valve is at rest

Normally

Closed

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Valve Description


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Symbols

Directional

Control Valves

3 position valves

Closed centre

Open

centre

Tandem centre

A B

P T

A B

P T

A B

P T

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Symbols

Directional

Control Valves

3 position valves Floating Centre

Regenerative Centre

A B

P T

A B

P T

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Symbols

Methods of Operation General manual operation

Usually used to represent a manualoverride

Lever operation

Foot Pedal operation

Push Button operation

Detent operation

Usually used with lever operation

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Symbols

Methods of Operation

Roller operation

Spring operation

Usually used as a return or centring

function

Solenoid operation

Internal pilot or 2 stage

operation

Usually used with solenoid

operation

Pilot operation

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Symbols

Non return valves

FreeOpens if inlet pressure is

higher than outlet pressure

Spring loaded Opens if inlet pressure is higher

than outlet pressure plus spring

load

Pilot operated Can be opened to permit reverse

flow by means of pilot pressure

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Symbols

Pressure Controls

Pressure Relief

Valve

Single stage with internal drain

With external drain

Also sometimes represented so

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Symbols

Pressure Controls

Pressure Relief

ValveRemote pilot control with

internal drain

Internally piloted or 2 stage

relief valve

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Symbols

Pressure Controls

Pressure

Regulating ValvesDownstream pressure

control Forward flow only

external drain

A

B

3 way pressure

regulating valve

Downstream pressure control.

If outlet pressure exceeds set

pressure, flow is diverted to

tank.

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Symbols

Pressure Controls

Pressure regulator with reverse

flow by-pass built in

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A

B

Symbols

Pressure Controls

Pressure Relief Pressure Regulator

Shown normallyclosed Shownnormally open

Pressure

operation frominlet

Pressure

operation fromoutlet

Valve is closed until the pressure at the

inlet is high enough to open it (set

pressure). Flow is then usually to tank.

Valve is open until the pressure at the

outlet is high enough to close it (set

pressure). Flow is usually to cylinder or

other part of the circuit.

Comparison


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Symbols

Pressure Controls

Sequence Valves Maintains upstream pressure,

allows flow through to other

functions.

Two stage sequence

valve

Maintains upstream pressure,

allows flow through to other

functions.

External drain

Counterbalance valve

Provides controlled backpressure

for load support.

With built in by-pass

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Symbols

Flow

Controls

Non pressure

compensated

Flow proportional to preset area times

the square root of the pressure drop

across restrictor

Flow restricted in one direction only.

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Symbols

Flow

Controls

Pressure

Compensated

Flow proportional to preset areairrespective of valve pressure

drop. Direction of flow as indicated

(non reversible). Excess flow must

find alternative path.

Pressure &

Temperature

Compensated

Preset area automatically

adjusts to compensate for

viscosity changes

Bypass Regulator Excess flow bypassed

internally

Also sometimes

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Symbols

Flow

Controls

Flow divider Input flow is divided to 2 flows of

fixed ratio

Pressure compensated.

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Symbols

Proportional Valves

Valve with 2 distinct operating positions,fully open and fully closed, and an

infinite number of intermediate

positions.

4/3 directional control valve, proportional.

3 distinct operating positions with closedcentre position and an infinite number of

intermediate positions.

Solenoid current is controlled through

proportional amplifier.

Servo valve

Controlled by a torque motor.

Direction of movement is dependent on

voltage polarity.

Amount of movement is dependent on

magnitude of current.Page 32


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Symbols

Modulating Control

Valves

More often referred to as Proportional Control Valves and usually solenoid operated.

With these valves there is a known relationship between the position of the spool and

the flow through the valve. Therefore flow (speed) can be controlled electronically

without the need for adjusting manual valves.

Spool Travel

FlowRate

Full flow

Proport ional Valve

Conventionalvalve


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Symbols

Miscellaneous

Reservoirs Vented to atmosphere

Return line below fluid level

Return line above fluid level

Header tank

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Symbols

Miscellaneous

Conditioning UnitsFilter or Strainer

Cooler

Water cooled

Heater

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Symbols

Miscellaneous

Shut off valve

Accumulator

Gas type

Pressure Gauge

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Hydraulic Formulae


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Force (F) = Area (A) x Pressure (P)

Newtons (N) Square metres (sq. m) Pascals (Pa)

Pounds (lbf) Square inches (sq. in) Pounds/sq.in (psi)

Note:* The pascal is a very small unit of pressure.

100 Kpa= 10N = 14.5 psi = 1 Bar

cm2

e.g. 5000KPa = 50 Bar = 725 psi

F = A x P P = F A = F

A P

-------------------------------------

Hydraulic Formula

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Flow Rate = Flow Velocity x Flow area

metres 3 / sec metres / second metres 2

Usually flow rate is given in Litres/minute and flow area given in cm2 or mm2 .

Care must be taken to ensure the correct multiples are used.

Eg. Calculate the cross sectional area required for the suction line of a pump

delivering40 l/min with a maximum flow velocity of 1.2 m/s.

Area = Flow rate 40 l/min = 40/60 x 10-3 m3/s

Flow velocity

Area = 40 x 10 -3 m2

60 x 1.2

Area = 0.555 x 10 -3 m2 (Pipe bore of 26.6mm)--------------------------------------------------------------------------

Volume of cylinder (base end) = Piston area x stroke length

Volume of cylinder (rod end) = (Piston area - Rod area) x strokelength

Hydraulic Formula

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Hydraulic Formula

Work done = Force x distance moved

Force on a piston = Pressure x area of piston

So,

work done = Pressure x area x distance moved

Area x distance moved= Volume

So

Work done = Pressure x volume

Power is the rate of doing work or, work done per unit of time.

Volume per unit time is flow rate - m3/second

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Hydraulic Formula

So

Hydraulic power = Pressure x Flow rate

If pressure is in Pascals (N/m2) and the flow rate is in m3/second then

Hydraulic power = Pressure x Flow rate - (Nm/s) = Watts

It is usual to give flow rate in litres/minute and pressure in bars. To use

these units in the calculation the following conversion has to be made.

Hydraulic Power (kW) = Pressure (bar) x Flow rate

(l/min)

600

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Bar x 100,000 x Flow rate (L/min) = Power in kilowatts60,000,000

To calculate power in Watts the following formula can be used

Pressure x Flow rate = Power

N x m3 = Nm = Watts

m2 sec sec

To use more useful units.

Bar times 100,000 = N/m2 L/min divided by 1000 then divided by 60 = m3/sec

So Bar x 100,000 x Flow rate (L/min) = Power in Watts

60,000

Pressure (Bar) x Flow rate (L/min) = Power in kW

600


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1) If a system pressure of 3000 p.s.i acts on a piston area of 3 sq ins, (approx 2 ins

diameter) what force will be produced?

2) If a force of 10,000 lb is produced from a cylinder with a piston area of 2.5 sq ins, what

is the pressure build up in the system?

3) If a force of 15,000 Newtons is produced in a cylinder with a piston area of 20 sq cm,

what is the pressure build up in the system?

4) A cylinder with piston area 150 sq cm and stroke length of 400cm must fully extend in 15

seconds. What flow rate (in Litres/min) must the pump deliver to achieve this?

5) If a hydraulic pump is delivering a flow of 40 litres / min against a pressure of 150 bar,

what is the power consumption (in KW) at the pump?


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Method of Return

Method of Operation

(Number of Boxes)

Number of Control positions

Number of Ports

Normally closed

or Normally open


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x y


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A1 A2 A3

B1 B2 B3

P T


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A1

A2

A3

B1

B2

B3

P T


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A1 A2 A3

B1 B2 B3

P T


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A1 A2 A3

B1 B2 B3

P T


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A1 A2 A3

B1 B2

P T

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هيدروليك

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A1 A2 A3

B1 B2

P T

تبريز – ير ن

:09144142432تلفن همر ه

فكس

:3802509-0411

Intro to Hyd Symbols (1)

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